View Full Version : "cheap" dehumidifier replacement for poolhouse. Question / advise

11-08-2014, 05:15 AM
Location: Netherlands. The advise i would like to get is not nessecerely a brandname and product type, but an advice if this will this work.
At this time our dehumidifier for the poolhouse broke down again. It suffers from the enviroment it has to clean up. Not doing a good job from the start of its life. Meaning we were disapponted about its capacity.
It is of the combination type, meaning it can provide hot air as well. This setting is not used because the pool generates enough heat. 3 fase 220v about 3 Kw professional unit.
List price at the moment is 5000 euros. Makes a lot of noise.

Rather than replacing it with a similar machine and undoubtly facing the same problems we would like to try the portable variant and run it into the ground.
Airco service is about the same yearly cost as a cheap unit. About 250 euros.
I would need to connect a hose to the condense container to be able to leave it unattended.
Great but is does a refrigirated cheap unit work at a temperature of 30 degrees Celcius air temperature and 28 degrees water temp. Or does it only work at cellar temperatures.

At this moment the circuitboard broke down yet again. At a price of 300 euros + repair fees we would be stuck with this old machine and its problems.
Can not keep up yet overspecked, and does not survive this hot clorinated salt water environment. Oil is used to keep evaporation to a minimum. Display of oil dispencer: broke down due to mentioned above.
Due to lack of space it is situated in the poolhouse itself. Electronics the lot.

Price wise it seems like a good choice to get a cheap machine and hope it lasts for a year. It would be less than ethical to claim warranty.
But will it do its yob during this year.

11-08-2014, 10:50 AM
I believe that dehumidifiers aren't used in pools. Usually humidity mitigation is through air movement. Huge volumes of air are replaced by large air handling units in large pools. Can you improve the air exchange within your pool? A small volume,residential dehumidifier will chug along for a while certainly, but dehumidifying a pool seems a pointless job. A fan,or air to air heat exchanger will be the most effective.

J Tiers
11-08-2014, 10:53 AM
That whole idea seems like a loser all around if it is an indoor pool. A large surface area of warm water is going to evaporate a LOT of water if you try to keep down the humidity of the room it is in. That is a matter of vapor pressures. The more water you pull from the air, the faster it evaporates.

If this is for an area connected to the pool enclosure with a door between, or a building near an outdoor pool, then it makes sense. You have some chance of actually changing the humidity.

11-08-2014, 11:11 AM
I agree with Jerry. If it's near the pool, then a unit as you describe is a lost cause.

I have had a couple of different portable dehumidifiers. The first provided both AC and Dehumidification. Rated at 70 pints per day. Worked fine BUT it was relatively inefficient - 1500w. Nicely heated the barn with the waste heat. The second (just installed) is dedicated dehumidifier (no A/C cycle). It uses 1/3 of the power for the same result.

The problem is usually at low temperatures (64F for my AC unit, 41F for my dehumidifier), but mine has a max temp rating of 85F degrees.

You might be better looking at another system - 0ne that uses (even heats) the COLD outside air and uses it as a dry air source to remove humidity from the interior air. Cold air (say 30-40F) when raised to room temperature temperature drops it's humidify dramatically. You probably want some type of heat recovery unit at the exit.

11-08-2014, 11:20 AM
Air to air heat exchanger, two fans, simple controls, lots of plastic honeycomb for transferring heat from exhaust air to intake air, drain hose for condensate.

11-08-2014, 01:45 PM
Poolhouse was a bit of a fib or it is because of my language barrier. It is a 4 x 4 meter building with a pool in it that is just a bit smaller. Swimming is done against a broad stream of water generated by a 48 volt motor vertically mounted like a ducted fan. You don't have to put up a balancing act to stay in this stream like the old fashioned jetstream systems. Olympic level swimming is possible at 75% of its capacity. At the moment of construction it was experimental because of its size, shape and compexity.
Because of the high water temperature there will be big drops of water hanging from the ceiling in no time turning the site into a mushroom cave. Up till recently the dehumidifier would drop the moisture level to 85% in combination with "heatsaver".
Heatsaver is a liquid product that forms an oil film on the water that keeps the water from evaporating and is compatible with the filter system. Because of lack of space the pool was literally shoehorned into this strangely shaped building and does not accept a poolcover.
The situation is not perfect but works to our satisfaction exept for this machine.
Chuffing along does not sound that bad but at 1500 w that would mean 10 euros of electricity a day. Learning from your experience your portable unit did not die.
And dryer used by builders to dehumidify plastered construction could have a better life expectancy due to inherent rough handling. A little more expensive.
An air to air heat exchanger does not sound verry different compared to a regular dehumidifier in this setup.
We always felt the old unit is a bit of a lemon so estimating the needed capacity turn into guesstimating.

Black Forest
11-08-2014, 03:01 PM
Why can't you cover the pool with a pool cover?

11-08-2014, 03:33 PM
An air to air heat exchanger does not sound very different compared to a regular dehumidifier in this setup.

Sounds like you blew off the suggestion without even looking at the specs. for one on the Internet.
No compressor, just two fans and control circuits. No high energy draw, used in topical fish stores and in Aquaculture labs.

Save the energy and the pool chemical, drain your little pool.

11-08-2014, 04:57 PM
1500w = 10 euros/day.. wow... I pay about 8-12c a kw/hour, so that's $4.32 absolute worst case, or roughly 3.1 Euros. My current dedicated portable dehumidifier (not a portable A/C, but it still has a pump and refrigerant) uses about 500w, so 1 Euro a day, and I'm too cheap to keep it running the entire time (even though it's set to maintain 50 % humidity).

In your case (pool of warm water)you need to look at the cool outside air as your best solution (for the winter), and source a suitable system.

BTW.. Chlorine in the air is a disaster for most consumer electronics.

11-09-2014, 03:51 AM
i am with rosco-p, air to air heat exchanger.
but unless you find a way to minimize evaporation it will all be more or less futile

11-09-2014, 05:50 AM
Because of the odd shape a mechanical operated cover is not possible. Also there is about 5 cm, with the exception at the place you enter, around the pool boarding the mirrors and double glazing to the outside. A floating divice has got no place to stay during exercise and to much of a hassle after a certain age. This is way we use the oil. The moment you poor it onto the water the fog disappears.
With helping build this pool i went into the deep end, technology wise. That is why an air to air heat exchanger looks the same to me. Would have to make a hole in the roof to install this. Not a problem. Going to look into this.
We are paying through the nose for everything around here. Energy bills consist mostly of taxes.
With this less than ideal machine that broke down recently the climate changed from swimming in a poolhouse with a view at a garden into swimming in the rain with steamy windows.
Changing to an other system takes research time. Meanwhile pool is empty.

How much would an air to air system cost without installation. (don't want to be with the timing chain nay sayers:o)

Black Forest
11-09-2014, 07:17 AM
When I was a kid my father built me a model train platform in my bedroom. It raised to the ceiling when not in use. On the bottom of the platform was the light for the bedroom. All I had to do was push a button and the train platform lowered from the ceiling down to usable height. The legs folded up after it was partially raised.

You might be able to do something like that for your pool. Simple frame with vinyl covered Styrofoam and some pulleys, rope and a capstan winch.

Paul Alciatore
11-09-2014, 11:27 AM
I like Black Forest's idea.

I also like the idea of just bringing in outside air. You may not need a lot of it to remove the humidity.

Another thought: it seems that the problem is the chlorine in the air is destroying the circuitry. There is no reason why the circuitry must be exposed to the pool room's air. You could either enclose the unit and duct in some outside air to ventilate it OR move the unit out of the room and duct the pool room air to and from it.

11-09-2014, 11:42 AM
A poolcover would be extremely difficult due to the shape of the roof and building. It is possible after spoiling lots of material making prototypes.
This idea was rejected years ago. I will give this another try.
There is still the nessecity to dry the concrete stairs around the basin. 2 sq/m.

11-09-2014, 01:25 PM
Another thought: it seems that the problem is the chlorine in the air is destroying the circuitry. There is no reason why the circuitry must be exposed to the pool room's air. You could either enclose the unit and duct in some outside air to ventilate it OR move the unit out of the room and duct the pool room air to and from it.

You could embed the circuitry in potting compound.

Black Forest
11-09-2014, 01:39 PM
A poolcover would be extremely difficult due to the shape of the roof and building. It is possible after spoiling lots of material making prototypes.
This idea was rejected years ago. I will give this another try.
There is still the nessecity to dry the concrete stairs around the basin. 2 sq/m.

How about a picture of the building and what you are having to deal with inside?

11-10-2014, 07:53 AM
Because of the high water temperature there will be big drops of water hanging from the ceiling in no time turning the site into a mushroom cave.

Is this the "real problem" or do you have a different real problem?

What I'm getting at is warm water doesn't magically produce condensation. A surface that's colder than the local dew point causes condensation. A surface thats warmer than the local dew point cannot condense. Often its enormously cheaper to slightly warm a solid than to process enormous amounts of gas.

Your strategy of trying to lower the dew point is unlikely to work long term or work efficiently, seeing as you have a giant water vaporizer as the floor of the "room". Like trying to make low humidity inside a steam engine boiler while its operating. What would probably work excellently is dumping a bit of heat into the walls / ceiling. Doesn't have to be as elaborate as a full hydronic heating system. You're not trying to build a sauna either. You just need the walls/ceiling to be one degree warmer than the dew point, which probably approaches the pool temperature at times.

Your water temperature sounds coldish. If you were in the 30s like a hot tub you'd have real problems heating the walls to 40s and causing heat exhaustion or maybe people burning themselves, but a mere 28 isn't that bad. People can swim in 29 degree air in the tropics, right?

The only other comment I can think of, is this doesn't eliminate the need for ventilation, think of the chlorine if nothing else. Also you need to keep an eye on the innards of your air handlers... mold doesn't grow very well on bone dry warm walls no matter the dew point in my experience, but who knows what'll be growing inside the air handlers for heat recovery ventilator or the condensate drainage lines or whatever. Or rephrased a mixed approach would likely work well. Eliminate 99% of the condensation by heating the walls and ceiling and run a cheap smaller dehumidifier unit.

I would be shocked if your pool exceeded 8000 gallons (I donno 30 kilo-liters or so?) and uninsulated food grade fiberglass water tanks cost maybe a buck a gallon delivered. May be some issues with temp and chlorine. Some pool structure and liner designs will be destroyed if alternating empty/full, some don't care. But if its a private residence and the pool is unused 99% of the time, just in energy savings alone, storing all that water in a sealed heavily insulated tank 99% of the time would save an enormous amount of energy and pay for the tank and piping in possibly only a year. You can and should plumb the tank to continue to heat and treat and filter the water inside the tank. Just don't go leaping into the pool without checking if the water is in the pool or the tank LOL.

Time to misquote Black Forest: "How to become a millionaire: Start out with 10 million and take up pool ownership as a hobby!"

11-10-2014, 12:33 PM
For privicy reasons i would rather not put pictures on the net.
I am not going to pot at this moment. Found the ventilator motor was humming. Seals stuck on axle. Gave the squirle cage a wirl. Guess this send a signal to the circuit board to do something. Ac compressor started and produced cold air.
Jippi. Afraid to touch the electronics. Going to fiddle with the bearings.
The concrete floor is porous and acts as a sponge. Good point. Got some sealer left specially for this purpose.
During summer, this is what we call it, the doors are left open. Makes all the difference and reduces the problem with about 2 to 3 months.
For winter i welded stainless steel radiator elements hooked to the central heating system heating the air. The clumsy bastard central heating mechanic thought he could hook them up with galvanised piping in a salt water pool.
He said it took him so long to cut the stainless i provided so he did it his way. YOUR FIRED!
As long as the setting of the chlorinator are right all the chlorine that is made gets dissolved in the water and turns into salt again after reaction with debris then caught in a filter cartrige. Not to much clorine smell.
Pool was welded from 1 cm thick PE sheet and insulated with 2k hard pu foam. You can take the water out as many times as you like. Indestructable but scratches easyly. 10.000liters.
If this dehumidifier likes to run for another few months there is some time to work out a durable solution.
Space is at a premium over here. No space to put a storage tank that big in the garden. Also not a good idea for the swimming machine. The motor is suspended in the water. More temperature fluctiation will lead to a bigger vacuum in the motor that draws in water.
On the other hand, if you would put the inverter of the swimming machine at 100% duty cycle it will dump the content of the pool in 5 seconds over the side.
On installation we blew out a quart of the content to where i was standing. That was fun.

11-10-2014, 05:53 PM
I've seen pools in cold climates that are covered with ping-pong balls to prevent heat loss- you can swim right through them or sweep them out with a net very quickly. They're cheap, light, and will cover any shape pool.

11-11-2014, 12:02 PM
At old age swimming in a basin filled with balls again. Wonder how long they would last. A bit like the polystyrene balls the use on wells in africa to keep the mosquitos out.
Would need a mesh for the skimmer.

11-11-2014, 12:43 PM
This type of indoor pool is hardly a new innovation, what do other owners do to keep the humidity down to a reasonable level in their pool house? I think inquiring with one or more dealers/installers of such would reveal what the current solution is.

Paul Alciatore
11-11-2014, 03:48 PM
Or just plastic bags. But neither would work for all the wiring. Perhaps some silicone caulk on the connections.

You could embed the circuitry in potting compound.